Lyft will suggest a donation for drivers. Passengers could pay less, but drivers could also refuse to pick them up if they did. Now, Lyft is removing all doubts about how much you should pay by enforcing mandatory pricing.

Lyft cars are unmistakable with those giant pink moustaches fastened to their hoods.

"And I'd tap the app and a driver would show up," San Francisco resident Karen Tse said.

Tse liked the way she could use her smartphone to summon a driver.

"It's good because I was able to pay them my, what I think they deserve," she said.

A suggested donation would appear on her smartphone. Tse sometimes paid a little less, but it cost her later on.

"Every single time I went onto the app, it said no drivers available," she said.

Tse says no one from Lyft would give her a lift. Later she saw a notice on an old receipt that read, "low donations may make it hard for you to get rides in the future."

Lyft told 7 On Your Side that drivers can screen passengers with a history of low payments.

"We're transitioning from donations to regular payments in California, providing peace of mind to drivers and more transparency to passengers."

A spokesperson did not respond to our request for an on camera interview. But here's the new pricing: The company will calculate fares based on rates of $1.90 per mile and 40 cents per minute. It will charge a $2.50 pickup fee and $1 to cover insurance.

By contrast, San Francisco taxis charge $2.75 per mile, 55 cents for each minute stuck in traffic or waiting and there is a $3.50 charge at pickup.

Also, Lyft is now adding a prime time tip for drivers during peak hours. Tips will start at 25 percent of fare, depending on demand. For example, on New Year's Eve, the company charged a $23 tip for this $19 ride.

Lyft tells customers:

"Prime time will happen automatically when passengers requesting rides outnumber drivers on the road. Passengers will see a clear notification showing the percent tip before confirming a ride request."

Tse says she's OK with the set pricing.

Last year, the California Public Utilities Commission ruled the rideshare companies do not need to be regulated like taxis and limousines, but can operate as networking companies. Now a taxicab association is appealing that ruling at the PUC.